[Ceilometer]: cpu_util meter not being calculated as expected leading to delay in scaling

Trinh Nguyen dangtrinhnt at gmail.com
Fri Apr 26 02:01:25 UTC 2019

Hi Arvind,

Could you please tell us which release of Ceilometer that you are referring


On Wed, Apr 24, 2019 at 4:55 PM Arvind Kumar <Arvind.Kumar at ril.com> wrote:

> Hi,
> A design issue is observed in ceilometer service of Openstack. Setup
> include multiple compute nodes and 3 controller nodes. Meters from each
> compute node are sent to all the 3 ceilometer instances via RabbitMQ in
> round robin fashion at an interval of 10 min. After transformation of
> cumulative cpu  meter data, cpu_util is generated by ceilometer instance at
> controller node and is published to the http address configured in
> ceilometer pipeline configuration. cpu_util is used by the application to
> take the decision if scaling of VM needs to be triggered or not.
> Ceilometer instance calculates cpu_util for a VM from the difference
> between cumulative cpu usage of VM at two timestamp divided by the
> timestamp difference. Let’s say 1 compute node send the cumulative cpu
> usage of a VM (C1, C2, C3, C4) at timestamp T1, T2, T3, T4 (difference
> between any two timestamp is 10 min). Now (C1,T1) & (C4,T4) tuple is
> received by ceilometer instance 1, (C2,T2) by instance 2, (C3,T3) by
> instance 3. Here even if CPU usage of VM is increased between T1 & T2,
> cpu_util is calculated for 30 min duration (T1 & T4) rather than as
> expected for 10 min. This leads to scaling getting triggered after T4 that
> too when CPU usage is consistently above the threshold between T1 and T4.
> Please suggest how could this issue could be resolved. Do we have any
> solution to bind VM or compute node meter data to specific ceilometer
> instance for processing?
> Regards,
> Arvind.
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